The present invention relates to a phase and frequency variable oscillator which can adjust both phase and frequency of the output signal independently from each other control value without time delay.
One of the prior variable oscillators is a voltage controlled oscillator (OSC) which adjusts the frequency in order to obtain the desired phase. When the phase output of FIG. 1(a) is desired, the control voltage (b) as shown in FIG. 1(b) is applied to the voltage controlled oscillator. Then, the output phase leads or laggs as shown in FIG. 1(c). When the phase reaches the desired value, the control voltage is stopped as shown in FIG. 1(b). However, a voltage controlled oscillator as shown in FIGS. 1(a) through 1(c) has the disadvantages that some time delay T.sub.d is inevitable in order to reach the desired phase and no step change of the phase without time delay is obtained. Furthermore, the accuracy of a voltage controlled oscillator is not satisfactory.
Another prior type is an endless phase shifter as shown in FIG. 2, in which reference numeral (1) is an input terminal, (2) is a quadrature hybrid circuit for providing a pair of quadrature phased outputs, (3) and (4) are mixers, (5) is a control signal input terminal, (6) is a control circuit for providing DC voltages (11) and (12) related to the control signal (5), (7) is an in-phase power combiner, and (8) is an output terminal.
Assuming that the input signal at the terminal (1) is; EQU A(t)=a' sin (2.pi.f.sub.0 T+.phi..sub.0 ')
then, the outputs (9) and (10) of the quadrature hybrid circuit (2) are;
Signal 9 a sin (2.pi.f.sub.0 t+.phi..sub.0) PA1 Signal 10 a cos (2.pi.f.sub.o t+.phi..sub.0) PA1 Signal 11 b cos .theta. PA1 Signal 12 b sin .theta.
where (a) and (.phi..sub.0) are determined by (a') and (.phi..sub.0 '). When a phase lead of .theta. is desired, the control signals (11) and (12) of the control circuit (6) are shown below.
The output signal at the output terminal (8) is shown below. ##EQU1##
The output signal B(t) has a phase lead of .theta. with respect to the input signal A(t).
Although a prior endless phase shifter can adjust the phase of a signal arbitrarily, it has the disadvantage that the frequency of the signal is not adjusted.